Central pathways of some autonomic reflex discharges

SUMMARY1. A study has been made of the effect of spontaneous and induced muscle spasms on blood pressure, heart rate, hand blood flow, calf blood flow and occluded vein pressure in the hand and foot in non-bedridden patients with chronic, closed, complete, localized transaction of the cervical spinal cord.2. Both types of spasm produced a similar response consisting of an increase in blood pressure and occluded vein pressure and a decrease in heart rate and hand and calf blood flow. The changes commenced within 2-3 see and usually reached maxima in 20-30 sec. On some occasions there was a temporary initial increase in heart rate and calf blood flow.3. The changes occurred independently of changes in bladder pressure. 4. It is concluded that the changes in peripheral blood vessels result from a spinal sympathetic reflex to somatic afferents associated with muscular contraction.

Section: Introductionmentioning

confidence: 60%

Cardiovascular changes associated with skeletal muscle spasm in tetraplegic man

Corbett¹,

Frankel²,

Harris³

1971

“…When the spinal cord was intact, F 104 W. C. DE GROAT AND R. W. RYALL the latency of reflex excitation was sufficiently long to allow for conduction of impulses to and from the brain-stem and it is suggested that the reflex is a long-loop reflex involving supraspinal centres. Similar, longlatency responses in the sympathetic (Coote & Downman, 1966) and somatic (Shimamura et al 1964) nervous systems have also been attributed to reflexes involving supraspinal centres. However, the possibility that the late reflex discharge of sacral parasympathetic neurones is a spinal reflex which depends upon a tonic descending facilitation has not been entirely excluded.…”

Section: Discussionmentioning

confidence: 83%

Reflexes to sacral parasympathetic neurones concerned with micturition in the cat

Groat¹,

Ryall²

1969

256

129

SUMMARY1. Reflexes to sacral parasympathetic neurones were studied by electrophysiological techniques in decerebrate, in chloralose-anaesthetized, and in chronic spinal cats.2. Excitatory reflexes from pelvic nerve and sacral somatic afferent nerve fibres were present before and after chronic transection of the spinal cord, but the latencies differed markedly. It was concluded that the longlatency reflexes observed when the spinal cord was intact involved longloop reflexes to the brain-stem. The weak, short-latency reflexes in the chronic spinal cat were never observed when the spinal cord was intact and could be due to reorganized spinal connexions. The short-latency reflexes are probably unimportant in normal micturition.3. Stimulation of afferent fibres in the pelvic or sacral somatic nerves produced short-latency inhibitory post-synaptic potentials (IPSPs) and inhibition of discharges in parasympathetic neurones. This inhibition was due to a spinal reflex. 4. A local reflex was demonstrated in the pelvic plexus. This was probably a cholinergic axon reflex, but the remote possibility that it was a local cholinergic reflex involving sensory neurones in the bladder wall has not been excluded.

“…For this purpose, the tip of a cooling probe (2-5 mm o.d.) maintained at 0°C, similar to that described by Coote & Downman (1966), was placed on the floor of the fourth ventricle in the mid-line, 1-0 mm rostral to obex. A sequence of ten averaged spinally evoked responses was repeated 6 times before and then when the medulla had been cooled, and subsequently on recovery from cooling.…”

Section: Resultsmentioning

confidence: 99%

Mediation of baroreceptor inhibition of sympathetic nerve activity via both a brainstem and spinal site in rats.

Lewis

Coote

1994

1. The possible involvement of a spinal site of sympatho-inhibitory action in the baroreceptor reflex pathways was investigated by determining the effect of phenylephrine-induced, baroreceptor-mediated inhibition on a spinally evoked excitatory response of renal nerve activity before, during and after removal of tonic descending excitatory drive from the rostral ventrolateral medulla (RVLM). 2. Stimulation of descending excitatory axons at the C4 vertebral level evoked a highly reproducible excitatory response (mean variance, 2'2 + 06%) in a renal sympathetic nerve with a latency of 72 + 5-7 ms and duration of 211 + 32 ms. 3. Following baroreceptor activation, the magnitude of this spinally evoked response was reduced by 33-5 + 4-2% compared with control spinal response. 4. To remove tonic descending excitatory drive, glycine was microinjected bilaterally into the RVLM (RVLM block); this briefly and reversibly abolished spontaneous sympathetic nerve activity. 5. Following RVLM block, the spinally evoked response in a renal sympathetic nerve was inhibited by 16-9 + 4'4 % during baroreceptor activation. 6. Intrathecal administration of the glycine antagonist strychnine to the lower thoracic segments of the spinal cord virtually abolished this inhibition. 7. It was concluded that baroreceptor inhibition of sympathetic activity occurs at a spinal site as well as a supraspinal one. Glycine is a likely mediator of the inhibition at the spinal site.